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From "marco polo (JIRA)" <j...@apache.org>
Subject [jira] [Created] (ACCUMULO-3508) Zoocache utilizes course grained locking causing unnecessary synchronization in many tserver ops
Date Thu, 22 Jan 2015 17:57:34 GMT
marco polo created ACCUMULO-3508:
------------------------------------

             Summary: Zoocache utilizes course grained locking causing unnecessary synchronization
in many tserver ops
                 Key: ACCUMULO-3508
                 URL: https://issues.apache.org/jira/browse/ACCUMULO-3508
             Project: Accumulo
          Issue Type: Sub-task
          Components: fate
    Affects Versions: 1.6.0
            Reporter: marco polo
            Priority: Minor
             Fix For: 1.6.3


Through jstacking I have observed busy tablet server threads waiting for the Zoocache to be
updated or even read. Profiling via yourkit indicates potential deadlocks when threads wait
for a long period of time ( in my case my waits were 10+s ) when many scans were running against
my instance.

My patch, which is forthcoming, removes synchronization and utilizes a reentrant read/write
lock (RERWL) to synchronize the maps. My initial design utilized concurrent hash maps, but
the design of existence becomes simpler and changes fewer by using the RERWL. 



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